There is a need for swellable and degradable microspheres for use as a degradable embolic material for embolization treatment. Embolization involves the introduction of a material into the vasculature in order to block the blood flow in a particular region. This procedure may be used to treat non-cancerous tumors, such as uterine fibroids, as well as cancerous tumors. Vascular occlusion in the case of tumors may be used to suppress pain, limit blood loss during surgery, or to cause tumor necrosis. In addition, embolization treatment may be used to control bleeding caused by conditions such as stomach ulcers, aneurysms, and injury.
Non-degradable hydrogel microspheres have been produced and used in tissue augmentation and embolization treatments (see for example, U.S. Pat. No. 6,218,440, U.S. Pat. No. 4,446,261, U.S. Pat. No. 6,436,424, JP1994056676A, and copending and commonly owned US Patent Application Publication Nos. 2007/0237956 and 2007/0237742). However, degradable embolic microspheres would enable the administration of a number of different therapies (e.g., drug delivery and surgery) to a site without permanently occluding the site from blood flow. This could lead to more effective therapies and better patient response to treatments.
Degradable hydrogel microspheres are known in the art. One type of degradable microsphere incorporates degradable crosslinks. As the crosslinks degrade, the microsphere breaks down into soluble polymer chains (see for example U.S. Pat. No. 6,713,646, U.S. Pat. No. 6,884,905, and WO 2003/094930). Another type of degradable microsphere is prepared from degradable polymers such as poly(lactide-co-glycolide) copolymers. The disadvantage of both types of microspheres is that they may degrade into small insoluble fragments, which could lead to detrimental health effects.
Consequently, there is a need for swellable and degradable microspheres for use in therapy, which do not degrade into small fragments. The present invention satisfies this need and provides a new process for preparing swellable and degradable microspheres.